Flexible substrate and fabrication method thereof, and flexible display apparatus

ABSTRACT

The embodiments of the disclosure disclose a flexible substrate, a fabrication method thereof, and a flexible display apparatus. The flexible substrate includes a first organic layer and an inorganic buffer layer stacked together. The first organic layer and the inorganic buffer layer form an organic-inorganic composite structure. The expansion coefficient of the flexible substrate provided by the embodiment of the present disclosure is more matched with that of the rigid auxiliary substrate, so as to reduce the risk of warping of the rigid auxiliary substrate and then improve the process accuracy when fabricating the display device.

RELATED APPLICATIONS

The present application is the U.S. national phase entry of theinternational application PCT/CN2017/090261, with an internationalfiling date of Jun. 27, 2017, which claims the benefit of Chinese PatentApplication No. 201610810819.3, filed on Sep. 8, 2016, the entiredisclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to the field of display technology, inparticular to a flexible substrate, a fabrication method thereof, and aflexible display apparatus.

BACKGROUND

A display apparatus is an apparatus for displaying a picture, such as acharacter, a number, a symbol, a photo, or an image formed by acombination of at least two of a character, a number, a symbol and aphoto. At present, display apparatuses can be divided into rigid displayapparatuses and flexible display apparatuses. The flexible displayapparatuses have the advantages of good impact resistance, strong shockresistance, light weight, small size, and convenient portability, andhave drawn wide attention.

A flexible display apparatus generally includes a flexible substrate, adisplay device formed on the flexible substrate, and a flexibleencapsulation layer for encapsulating the display device. Whenfabricating a flexible display apparatus, a flexible substrate isgenerally formed on a rigid auxiliary substrate (such as a glasssubstrate), then a display device is formed on the flexible substrateand the display device is encapsulated by a flexible encapsulationlayer. Then the flexible substrate is separated from the rigid auxiliarysubstrate, thus a flexible display apparatus is obtained.

SUMMARY

The embodiments of the disclosure provide the following technicalsolutions.

According to a first aspect of the present disclosure, a flexiblesubstrate is provided. The flexible substrate includes a first organiclayer and an inorganic buffer layer stacked together. The first organiclayer and the inorganic buffer layer form an organic-inorganic compositestructure.

Optionally, the flexible substrate further includes a second organiclayer disposed on a surface of the inorganic buffer layer facing awayfrom the first organic layer.

Optionally, the material of the first organic layer and/or the secondorganic layer is polyimide, polyethylene naphthalate, polyethyleneterephthalate, polyarylate, polycarbonate, polyetherimide, orpolyethersulfone.

Optionally, the materials of the first organic layer and the secondorganic layer are both polyimide.

Optionally, the second organic layer is doped with inorganicnano-particles.

Optionally, the material of the inorganic nano-particles is siliconoxide, aluminum oxide or titanium oxide.

Optionally, the material of the inorganic buffer layer is at least oneof silicon oxide, silicon nitride and silicon oxynitride.

Optionally, the flexible substrate further includes a rigid auxiliarysubstrate disposed on a surface of the first organic layer facing awayfrom the inorganic buffer layer.

According to a second aspect of the present disclosure, a flexibledisplay apparatus is provided. The flexible display apparatus includesthe flexible substrate according to the technical solution describedabove, a display device and a flexible encapsulation layer. The displaydevice is located on a side of the flexible substrate facing away fromthe first organic layer. The flexible encapsulation layer is used toencapsulate the display device. The flexible substrate and the displaydevice are covered by the flexible encapsulation layer, and the displaydevice is encapsulated between the flexible substrate and the flexibleencapsulation layer by the flexible encapsulation layer.

According to a third aspect of the present disclosure, a method forfabricating a flexible substrate is provided. The method is used tofabricate the flexible substrate according to the technical solutiondescribed above. The fabrication method includes: forming a firstorganic layer on a rigid auxiliary substrate; and forming an inorganicbuffer layer on the first organic layer. The first organic layer and theinorganic buffer layer form an organic-inorganic composite structure.

Optionally, after the step of forming the inorganic buffer layer on thefirst organic layer, the fabrication method further includes: forming asecond organic layer on the inorganic buffer layer. The second organiclayer is doped with inorganic nano-particles.

Optionally, the step of forming the second organic layer on theinorganic buffer layer includes: providing a coating solution of anorganic material which forms the second organic layer; adding inorganicnano-particles to the coating solution, and mixing them uniformly; andcoating the coating solution mixed with the inorganic nano-particles onthe inorganic buffer layer, and curing the coating solution mixed withthe inorganic nano-particles to form the second organic layer.Alternatively, the step of forming the second organic layer on theinorganic buffer layer includes: providing a coating solution of anorganic material which forms the second organic layer; adding aprecursor of inorganic nano-particles to the coating solution, andmixing them uniformly; coating the coating solution mixed with theprecursor of inorganic nano-particles on the inorganic buffer layer, andcuring the coating solution mixed with the precursor of inorganicnano-particles, converting the precursor of inorganic nano-particlesinto inorganic nano-particles to form the second organic layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrated herein are used to provide a furthercomprehension of the present disclosure and constitute a part of thepresent disclosure. The exemplary embodiments and the illustration ofthe present disclosure are used to explain the present disclosure, andare not intended to limit the present disclosure. In the drawings:

FIG. 1 is a structural schematic diagram of a flexible substrateprovided by an embodiment of the present disclosure;

FIG. 2 is a structural schematic diagram of another flexible substrateprovided by an embodiment of the present disclosure;

FIG. 3 is a comparison chart of the deformation rates of a flexiblesubstrate provided by an embodiment of the present disclosure, asingle-layer organic flexible substrate and a glass substrate atdifferent temperatures;

FIG. 4 is a structural schematic diagram of a flexible display apparatusprovided by an embodiment of the present disclosure;

FIG. 5 is a flow chart of a method for fabricating a flexible substrateprovided by an embodiment of the present disclosure;

FIG. 6 is a flow chart of a method for fabricating a flexible substrateprovided by another embodiment of the present disclosure;

FIG. 7 is a flowchart of a method for fabricating a flexible substrateprovided by yet another embodiment of the present disclosure; and

FIG. 8 is a flowchart of a method for fabricating a flexible displayapparatus provided by an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

In the related art, an expansion coefficient of a flexible substrate isusually much higher than that of a rigid auxiliary substrate, and thetemperature of the environment in which the rigid auxiliary substrateand the flexible substrate are placed usually changes during thefabrication of the flexible display apparatus. Therefore, when thetemperature of the environment in which the rigid auxiliary substrateand the flexible substrate are placed changes, the deformation rate ofthe flexible substrate is larger than that of the rigid auxiliarysubstrate, which easily leads to warping of the rigid auxiliarysubstrate, thereby resulting in a low process accuracy when fabricatingthe display device.

Therefore, it is desired to provide a flexible substrate, a fabricationmethod thereof, and a flexible display apparatus for solving thetechnical problem of low process accuracy when fabricating a displaydevice due to warping of a rigid auxiliary substrate.

In order to further illustrate the flexible substrate, the fabricationmethod thereof, and the flexible display apparatus provided by theembodiments of the present disclosure, details are described below withreference to the drawings in the specification.

With reference to FIG. 1, a flexible substrate 20 provided by anembodiment of the present disclosure includes a first organic layer 21and an inorganic buffer layer 22 stacked together. The first organiclayer 21 and the inorganic buffer layer 22 form an organic-inorganiccomposite structure. Specifically, when fabricating the flexiblesubstrate 20, the first organic layer 21 is formed on the rigidauxiliary substrate 10 first. Then the surface of the first organiclayer 21 facing away from the rigid auxiliary substrate 10 can becleaned and activated, e.g., by a plasma treatment. Then the inorganicbuffer layer 22 is formed and stacked on the first organic layer 21, andthe inorganic buffer layer 22 is in close contact with the first organiclayer 21. The first organic layer 21 and the inorganic buffer layer 22form an organic-inorganic composite structure.

The flexible substrate 20 provided by the embodiment of the presentdisclosure includes the first organic layer 21 and the inorganic bufferlayer 22 stacked together. The first organic layer 21 and the inorganicbuffer layer 22 form an organic-inorganic composite structure. There isan interface between the first organic layer 21 and the inorganic bufferlayer 22. Since the expansion coefficient of the inorganic material issmaller than that of the organic material, the expansion coefficient ofthe inorganic buffer layer 22 is smaller than that of the first organiclayer 21. Due to the effect of the interface, compared with the flexiblesubstrate formed with only the organic material, the expansioncoefficient of the flexible substrate 20 provided by the embodiment ofthe present disclosure is closer to the expansion coefficient of therigid auxiliary substrate 10. Therefore, the expansion coefficient ofthe flexible substrate 20 provided by the embodiment of the presentdisclosure is reduced and more matched with that of the rigid auxiliarysubstrate 10, so as to reduce the risk of warping of the rigid auxiliarysubstrate 10 and then improve the process accuracy and reduce theprocess error when fabricating the display device. Moreover, with theabove configuration, it is advantageous to fabricate a flexible displayapparatus of high resolution.

As shown in FIG. 3, a thermal mechanical analysis (TMA) is performed onthe flexible substrate 20 provided by the embodiment of the presentdisclosure, a single-layer organic flexible substrate and a glasssubstrate respectively. It can be seen that when the glass substrate isused as the rigid auxiliary substrate 10, compared with the single-layerorganic flexible substrate, the deformation rates of the flexiblesubstrate 20 provided by the embodiment of the present disclosure aremore matched with the deformation rates of the rigid auxiliary substrate10 (e.g. a glass substrate) at different temperatures. In particular, ata high temperature of 350° C. or higher, compared with the single-layerorganic flexible substrate, the deformation rates of the flexiblesubstrate 20 provided by the embodiment of the present disclosure aremore matched with the deformation rates of the rigid auxiliary substrate10 (i.e. a glass substrate) at different temperatures. Therefore, theflexible substrate 20 provided by the embodiment of the presentdisclosure can be more suitable for the high temperature requirementwhen fabricating the flexible display apparatus. For example, for aflexible display apparatus using the low temperature poly-silicon (LTPS)technology, a high temperature of 400° C. or a higher temperature isusually required during the fabrication. Since the deformation rate ofthe flexible substrate 20 provided by the embodiment of the presentdisclosure at a temperature of 350° C. or higher is more matched withthat of the rigid auxiliary substrate 10 (e.g. a glass substrate), forthe flexible display apparatus using the flexible substrate 20 providedby the embodiment of the present disclosure, warping of the rigidauxiliary substrate 10 can be prevented during the fabrication of theflexible display apparatus, so as to improve the process accuracy andreduce the process error when fabricating the display device.

With continued reference to FIG. 2, the flexible substrate 20 providedby the embodiment of the present disclosure further includes a secondorganic layer 23 disposed on a surface of the inorganic buffer layer 22facing away from the first organic layer 21. The second organic layer 23can protect the inorganic buffer layer 22 so that the stress on thesurface of the inorganic buffer layer 22 facing the first organic layer21 matches the stress on the surface of the inorganic buffer layer 22facing the second organic layer 23, thereby preventing the inorganicbuffer layer 22 from cracking due to the uneven stress. In addition, insuch an arrangement, the second organic layer 23, the inorganic bufferlayer 22 and the first organic layer 21 together form anorganic-inorganic-organic stacked structure. Due to the effect of theinterface between the first organic layer 21 and the inorganic bufferlayer 22 and the interface between the inorganic buffer layer 22 and thesecond organic layer 23, the expansion coefficient of the flexiblesubstrate 20 is further reduced, so as to further reduce the risk ofwarping of the rigid auxiliary substrate 10, and then improve theprocess accuracy when fabricating the display device.

In practical applications, the first organic layer 21 can include oneorganic material layer, and can also include a plurality of organicmaterial layers. The second organic layer 23 can include one organicmaterial layer, and can also include a plurality of organic materiallayers. If the second organic layer 23 includes a plurality of organicmaterial layers, inorganic material layers can also be interposedbetween the plurality of organic material layers. The inorganic bufferlayer 22 can include one inorganic material layer, and can also includea plurality of inorganic material layers.

In the embodiment of the present disclosure, the second organic layer 23is doped with inorganic nano-particles. Doping inorganic nano-particlesin the second organic layer 23 can increase the bonding effect betweenthe second organic layer 23 and the inorganic buffer layer 22, andprevent the interlayer separation between the second organic layer 23and the inorganic buffer layer 22. In addition, doping inorganicnano-particles in the second organic layer 23 can reduce the expansioncoefficient of the second organic layer 23, so as to further reduce theexpansion coefficient of the flexible substrate 20 and further reducethe risk of warping of the rigid auxiliary substrate 10, and thenimprove the process accuracy when fabricating the display device.

It is noted that the first organic layer 21 can also be doped withinorganic nano-particles to increase the bonding effect between thefirst organic layer 21 and the inorganic buffer layer 22, and preventthe interlayer separation between the first organic layer 21 and theinorganic buffer layer 22, while reducing the expansion coefficient ofthe first organic layer 21.

In the above embodiments, the material of the first organic layer 21 canbe selected from various kinds of organic materials such as polyimide,polyethylene naphthalate, polyethylene terephthalate, polyarylate,polycarbonate, polyetherimide and polyethersulfone. Optionally, thematerial of the first organic layer 21 is polyimide.

The material of the second organic layer 23 can be selected from variouskinds of organic materials such as polyimide, polyethylene naphthalate,polyethylene terephthalate, polyarylate, polycarbonate, polyetherimideand polyethersulfone. Optionally, the material of the second organiclayer 23 is polyimide.

The material of the inorganic nano-particles can be selected fromvarious kinds of inorganic materials such as silicon oxide, aluminumoxide and titanium oxide.

The material of the inorganic buffer layer 22 can be selected fromvarious kinds of inorganic materials. For example, the inorganic bufferlayer 22 can be silicon oxide, silicon nitride, silicon oxynitride,aluminum oxide, etc. Alternatively, the material of the inorganic bufferlayer 22 can be several of silicon oxide, silicon nitride, siliconoxynitride, and aluminum oxide. Optionally, the material of theinorganic buffer layer 22 can be at least one of silicon oxide, siliconnitride and silicon oxynitride. For example, the material of theinorganic buffer layer 22 is one of silicon oxide, silicon nitride andsilicon oxynitride. Alternatively, the material of the inorganic bufferlayer 22 can be silicon oxide and silicon nitride. For example, theinorganic buffer layer 22 includes a silicon oxide layer and a siliconnitride layer. Alternatively, the material of the inorganic buffer layer22 can be silicon oxide and silicon oxynitride. For example, theinorganic buffer layer 22 includes a silicon oxide layer and a siliconoxynitride layer. Alternatively, the material of the inorganic bufferlayer 22 can be silicon nitride and silicon oxynitride. For example, theinorganic buffer layer 22 includes a silicon nitride layer and a siliconoxynitride layer. Alternatively, the material of the inorganic bufferlayer 22 can be silicon oxide, silicon nitride and silicon oxynitride.For example, the inorganic buffer layer 22 includes a silicon oxidelayer, a silicon nitride layer and a silicon oxynitride layer.

In the above embodiments, the thickness of the first organic layer 21,the inorganic buffer layer 22, and the second organic layer 23 can beset according to actual requirements and actual fabricationcapabilities. For example, the thickness of the first organic layer 21and the thickness of the second organic layer 23 can be greater than orequal to 2 μm, the thickness of the inorganic buffer layer 22 can rangefrom 100 nm to 600 nm, and the thickness of the inorganic buffer layer22 can be e.g. 100 nm, 300 nm or 600 nm.

Optionally, the flexible substrate further includes a rigid auxiliarysubstrate 10 disposed on a surface of the first organic layer 21 facingaway from the inorganic buffer layer 22. In various treatment processes,the rigid auxiliary substrate can support the first organic layer, theinorganic buffer layer (and the second organic layer), so that varioustreatment processes can be performed on the flexible substrate. In thefinal stage of the fabrication, the first organic layer can be separatedfrom the rigid auxiliary substrate.

With reference to FIG. 4, an embodiment of the present disclosurefurther provides a flexible display apparatus, which includes theflexible substrate 20 according to the above embodiments, a displaydevice 30, and a flexible encapsulation layer 40. The display device 30is located on a side of the flexible substrate 20 facing away from thefirst organic layer 21. The flexible substrate 20 and the display device30 are covered by the flexible encapsulation layer 40, and the displaydevice 30 is encapsulated between the flexible substrate 20 and theflexible encapsulation layer 40 by the flexible encapsulation layer 40.

The advantages of the flexible display apparatus with respect to theprior art are the same as that of the flexible substrate describedabove, and details are not described herein again.

With reference to FIG. 5, an embodiment of the present disclosurefurther provides a method for fabricating a flexible substrate forfabricating the flexible substrate described in the above embodiments.The fabrication method includes the following steps: step S100, forminga first organic layer on a rigid auxiliary substrate; and step S200,forming an inorganic buffer layer on the first organic layer, the firstorganic layer and the inorganic buffer layer forming anorganic-inorganic composite structure.

In a specific implementation, in the step S100, a coating solution of anorganic material which forms the first organic layer such as a polyimidecoating solution, can be provided first. Then the coating solution ofthe organic material which forms the first organic layer is disposed ona rigid auxiliary substrate such as a glass substrate by coating,spraying, printing, etc. After the coating solution of the organicmaterial which forms the first organic layer is dried and cured, thefirst organic layer can be formed. After the formation of the firstorganic layer is completed, the surface of the first organic layerfacing away from the rigid auxiliary substrate can be cleaned andactivated by plasma treatment, to facilitate the close contact betweenthe inorganic buffer layer and the first organic layer. In the stepS200, after the formation of the first organic layer is completed, theinorganic buffer layer can be formed on the first organic layer by usinge.g. plasma enhanced chemical vapor deposition (PECVD). The inorganicbuffer layer is in close contact with the first organic layer, and thefirst organic layer and the inorganic buffer layer form anorganic-inorganic composite structure.

Each embodiment in this specification is described in a progressivemanner, and the same or similar parts in various embodiments can referto each other, and each embodiment focuses on differences from otherembodiments. Particularly, for the method embodiment, the description isrelatively simple because it is basically similar to the productembodiment, and for the relevant part, reference can be made to thedescription of the product embodiment.

In an embodiment of the present disclosure, the flexible substrate canfurther include a second organic layer stacked on the surface of theinorganic buffer layer facing away from the first organic layer. Withcontinued reference to FIG. 5, in the step S200, after the inorganicbuffer layer is formed on the first organic layer, the method forfabricating the flexible substrate provided by the embodiment of thepresent disclosure further includes a step S300: forming a secondorganic layer on the inorganic buffer layer, the second organic layerbeing doped with inorganic nano-particles.

In the above embodiments, the following two exemplary modes can beadopted for the step of forming the second organic layer on theinorganic buffer layer.

Mode 1: with reference to FIG. 6, in the step S300, the step of formingthe second organic layer on the inorganic buffer layer includes: stepS310, providing a coating solution of the organic material which formsthe second organic layer; step S320, adding inorganic nano-particles tothe coating solution, and mixing them uniformly; and step S330, coatingthe coating solution mixed with the inorganic nano-particles on theinorganic buffer layer, and curing the coating solution mixed with theinorganic nano-particles to form the second organic layer.

For example, the organic material forming the second organic layer canbe polyimide and the material of inorganic nano-particles can be silicondioxide. When forming the second organic layer on the inorganic bufferlayer, the polyimide coating solution can be provided first, then thesilicon dioxide nano-particles are added to the polyimide coatingsolution and uniformly mixed; and then the polyimide coating solutionmixed with the silicon dioxide nano-particles is coated on the inorganicbuffer layer by coating, spraying, printing, etc. After the polyimidecoating solution mixed with the silicon dioxide nano-particles is driedand cured, the second organic layer is formed.

The step of forming the second organic layer on the inorganic bufferlayer can also adopt the following mode.

Mode 2: with reference to FIG. 7, in the step S300, the step of formingthe second organic layer on the inorganic buffer layer includes: stepS310, providing a coating solution of the organic material which formsthe second organic layer; step S350, adding a precursor of inorganicnano-particles to the coating solution, and mixing them uniformly; andstep S360, coating the coating solution mixed with the precursor ofinorganic nano-particles on the inorganic buffer layer, and curing thecoating solution mixed with the precursor of inorganic nano-particles,converting the precursor of inorganic nano-particles into inorganicnano-particles to form the second organic layer.

For example, the organic material forming the second organic layer canbe polyimide and the material of inorganic nano-particles can be silicondioxide. In this case, the precursor of inorganic nano-particles can betetraethylorthosilicate (Si(OC₂H₅)₄). When forming the second organiclayer on the inorganic buffer layer, the polyimide coating solution canbe provided first, then tetraethylorthosilicate is added to thepolyimide coating solution and uniformly mixed; and then the polyimidecoating solution in which tetraethylorthosilicate is mixed is coated onthe inorganic buffer layer by coating, spraying, or printing, etc. Inthe process of drying and curing the polyimide coating solution in whichtetraethoxysilane is mixed, tetraethoxysilane undergoes in situ reactionin polyimide to form silicon dioxide nano-particles. With the silicondioxide nano-particles doped in polyimide, the second organic layer isformed.

With reference to FIG. 8, an embodiment of the present disclosurefurther provides a method for fabricating a flexible display apparatus,which includes the method for fabricating the flexible substratedescribed in the above embodiments. Specifically, the method forfabricating the flexible display apparatus includes: step S100, forminga first organic layer on the rigid auxiliary substrate; step S200,forming an inorganic buffer layer on the first organic layer, the firstorganic layer and the inorganic buffer layer forming anorganic-inorganic composite structure; optional step S300, forming asecond organic layer on the inorganic buffer layer, the second organiclayer being doped with inorganic nano-particles; step S400, forming adisplay device on the second organic layer; step S500, forming aflexible encapsulation layer on the second organic layer and the displaydevice; and step S600, separating the first organic layer from the rigidauxiliary substrate.

In the above embodiments, the display device includes a driving deviceand an OLED light emitting device. The driving device can be a thin filmtransistor, and the OLED light emitting device can include an anode, acathode, and an organic light emitting layer between the anode and thecathode.

In the above description of the embodiments, a particular feature,structure, material, or characteristic can be combined in any suitablemanner in any one or more of the embodiments or examples.

The above embodiments are only used for explanations rather thanlimitations to the present disclosure, the ordinary skilled person inthe related technical field, in the case of not departing from thespirit and scope of the present disclosure, may also make variousmodifications and variations, therefore, all the equivalent solutionsalso belong to the scope of the present disclosure, the patentprotection scope of the present disclosure should be defined by theclaims.

What is claimed is:
 1. A flexible substrate, comprising a first organiclayer, an inorganic buffer layer in direct contact with the firstorganic layer, and second organic layer disposed on a surface of theinorganic buffer layer facing away from the first organic layer; whereinthe second organic layer is doped with inorganic nano-particles.
 2. Theflexible substrate according to claim 1, wherein the material of atleast one of the first organic layer and the second organic layer ispolyimide, polyethylene naphthalate, polyethylene terephthalate,polyarylate, polycarbonate, polyetherimide, or polyethersulfone.
 3. Theflexible substrate according to claim 1, wherein materials of the firstorganic layer and the second organic layer are both polyimide.
 4. Theflexible substrate according to claim 1, wherein the material of theinorganic nano-particles is silicon oxide, aluminum oxide or titaniumoxide.
 5. The flexible substrate according to claim 1, wherein amaterial of the inorganic buffer layer is at least one of silicon oxide,silicon nitride and silicon oxynitride.
 6. A flexible display apparatus,comprising the flexible substrate according to claim 1, a display deviceand a flexible encapsulation layer, wherein the display device islocated between the flexible substrate and the flexible encapsulationlayer; wherein the flexible encapsulation layer is used to encapsulatethe display device.
 7. A method for fabricating the flexible substrateaccording to claim 1, comprising: forming a first organic layer on arigid auxiliary substrate; and forming an inorganic buffer layer on thefirst organic layer, the first organic layer and the inorganic bufferlayer forming an organic-inorganic composite structure; wherein afterthe forming the inorganic buffer layer on the first organic layer, themethod further comprises: forming a second organic layer on theinorganic buffer layer, the second organic layer being doped withinorganic nano-particles.
 8. The method for fabricating the flexiblesubstrate according to claim 7, wherein the forming the second organiclayer on the inorganic buffer layer comprises: providing a coatingsolution of an organic material which forms the second organic layer;adding inorganic nano-particles to the coating solution, mixing theinorganic nano-particles with the coating solution uniformly; andcoating the coating solution mixed with the inorganic nano-particles onthe inorganic buffer layer, and curing the coating solution mixed withthe inorganic nano-particles to form the second organic layer.
 9. Themethod for fabricating a flexible substrate according to claim 7,wherein the forming the second organic layer on the inorganic bufferlayer comprises: providing a coating solution of an organic materialwhich forms the second organic layer; adding a precursor of inorganicnano-particles to the coating solution, and mixing the inorganicnano-particles with the coating solution uniformly; and coating thecoating solution mixed with the precursor of inorganic nano-particles onthe inorganic buffer layer, and curing the coating solution mixed withthe precursor of inorganic nano-particles, converting the precursor ofinorganic nano-particles into inorganic nano-particles to form thesecond organic layer.
 10. The method for fabricating a flexiblesubstrate according to claim 7, further comprising: peeling the firstorganic layer from the rigid auxiliary substrate.
 11. The flexibledisplay apparatus according to claim 6, wherein the material of thefirst organic layer and/or the second organic layer is polyimide,polyethylene naphthalate, polyethylene terephthalate, polyarylate,polycarbonate, polyetherimide, or polyethersulfone.
 12. The flexibledisplay apparatus according to claim 6, wherein materials of the firstorganic layer and the second organic layer are both polyimide.
 13. Theflexible display apparatus according to claim 6, wherein the material ofthe inorganic nano-particles is silicon oxide, aluminum oxide ortitanium oxide.
 14. The flexible display apparatus according to claim 6,wherein a material of the inorganic buffer layer is at least one ofsilicon oxide, silicon nitride and silicon oxynitride.
 15. The flexibledisplay apparatus according to claim 6, further comprising a rigidauxiliary substrate disposed on a surface of the first organic layerfacing away from the inorganic buffer layer.